1. Field of the Invention
The present invention relates generally to a continuously or constant variable transmission (CVT) or clutch, and ortho-planar springs or compliant mechanisms.
2. Related Art
Some vehicles, such as snowmobiles and all-terrain vehicles (ATVs) utilize a transmission or clutch that is continuously or constantly variable. Such continuously variable transmissions (CVTs) or clutches provide an uninterrupted range of speed ratios, unlike a normal transmission that provides only a few discrete ratios. The transmission or clutch can include one or more pulleys, each with a pair of sheaves that move towards and away from one another to vary a diameter at which a belt engages the pulley. The linear movement of the sheave forms a variable diameter pulley. The linear motion of the sheave along the pivot is controlled by the speed of rotation of the pulley, torque on the transmission belt, and resistance from helical compression springs opposing the linear motion.
One disadvantage with helical compression springs is that they have only a single spring constant, making it difficult to tune for different operating conditions. Another disadvantage with helical compression springs is that they require relatively large space to accommodate the spring's minimum depth. Another disadvantage with helical compression springs is that they require a back plate to provide the spring reaction force on the pulley sheaves. Another disadvantage with helical compression springs is that some rotation or twisting occurs during their operation, thereby increasing friction, wear and noise.